Telephone switching system.



W. AITKEN. TELEPHONE SWITCHING SYSTEM.

APPLICATION FILED JUNE 9, 1913.

Patented Nov. 25, 1913.

3 SHEETS-SHEET 1.

W. A-ITKEN. E

TELEPHONE SWITCHING SYSTEM.

APPLICATION rum) JUNB9, 1913.

1,079,533. Patented Nov. 25, 1913.

8 SHEETS-SHEET 2 W. AITKBN.

TELEPHONE SWITCHING SYSTEM.

APPLICATION FILED JUNE 9, 1913. 1,079,533 Patented Nov. 25, 1913.

3 BKEETHHEBT 3.

I AI KEN, OF LlvnnrooL, ENGLAND.

unaware SWITCHING s s' r- Specification of Letters taunt.

Patented Nov. 25, 1913 Application filed June 9, 1913. Serial No 772,487.

To all whom it may concern:

Be it known that I, WILLIAM Arman, residing in Liverpool, England, have invented certain new and useful Improvements in Telephone Switching Systems, of which the following is a specification.

My invention relates to switching devices for use in connection with an extension line telephone and has for its object the provision of a switch by which connection can be extended through to the extension line, or whereby the master operator can estab lish connection either with the extension. line or with the exchange. Heretofore diflL; culty' has been experienced owing to the fact that oftentimes the master operator failed to restore the switching device to operative position upon the completion of a call.

The object of m invention is to provide a switch which is eld in operated position and is automatically restored to normal when the disconnect signal is given.

A further object of my invention is to provide a switch which 1s electromagnetically held in operative position.

A further ob ect is to provide a magnet having a novel form of pole-piece for controlling the switch.

Methods of carrying this invention into effect will now be described in connection with the accompanying drawings, in which Figure 1 is a front elevation of the apparatus employed at the intermediate station, part of the casing being broken away to show a detail of the apparatus. Fig. 2 is a side view of the twin switch with the ,controlling electromagnet. Fig. 3 is an end view of the electromagnet partly in section on the line 33 of Fig. 2. Fig. 4 is a diagram of connections, and Fig. 5 is another iagram of connections when a slow acting relay is employed as hereinafter referred to.

The apparatus at the intermediate station is combined in one casing for simplicity and cheapness, as shown in Fig. 1. The twin switch comprises two keys a and b of a wellknown pattern mounted with their frames 1 and 2 outward. If the key a is thrown lnto the position indicated in dotted lines (Fig. 2), it is automatically restored to normal when the key I) engages it on being moved'upward. When the key a has been moved upward to connect the attendants telephone, it is re-set by the arm 3 of a bellcrank lever (Fig. 1 and 4) engaging an extension 9 from the roller 5. This bell crank lever is operated by the switch-hook 4.

The key I) is controlled by the electromagnet 10, one pole 11 extending on one side of the key and the other pole 12 extending on the other side. The rollers 13 of the key 7) have a core of iron whose ends move freely in slots '17 in the pole pieces and engage with either end of each slot when moved either way to an operated position. When the key .7) is moved downward to cause springs 60 and 62 to engage respectively with springs 61 and 63, a circuit is completed through the coil of the electromagnet 10 and the rollers 13 having made contact with the upper ends of the slots in the pole pieces the key is held magnetically in that position until current is removed, when the key is restored to normal position by a spring (not shown). When key 6 is moved upward a similar result takes place.

Referring now to Fig. 4 the circuits and operation thereof will now be described. In this figure 0 represents the exchange, A is the intermediate station and A an extension substation. Should a call originate from the central exchange 0 the bell 18 will ring in the Well known manner, the circuit being from line 19, contact 20, contact 21, contact 22, contact 23, bell 18, condenser 24, contact 25, contact 26 to line 27. The attendant will move key a so that the roller 5 of that key causes contacts 20 and 28 and 26 and 29, respectively to make contact, when the exchange line will be extended to microphone 30 and receiver 31. The circuit is from line 19, contact 20, contact 28, microphone 30, receiver 31, contact 29, contact 26 to line 27. When the receiver 31 is replaced on the switch-hook 4 the arm 3 of the bell crank lever will engage with the extension 9 of the key a and reset this key, thereby opening the circuit and giving the clearing-out or disconnect signal at the central. Should however, the attendant desire to connect with extension substation A he will lift the receiver 31 and turn the generator 40, when a circuit will be completed from armature 41 to line 42, bell 43, condenser 44, contacts 45 and 46 of switchhook 47, short circuit of armature winding 48 of generator 49, to line 50. The key I) will then be moved so that contacts 60 and 61, 62 and 63, 64 and 65 respectively, are made, when the following circuit will be completed when the receiver is lifted at substation A, viz., battery B, contacts 66 and 67, contacts 62 and 63, line 42, microphone 51, receiver 52, contacts 53 and 46, shortcircuit of armature winding 48, line 50, electromagnet 10 with non-inductive shunt 68 in parallel with it, contacts 69 and 70, contacts 64 and 65, receiver 31, micro hone 30, contact 60 and 61 to the other side of the battery B. The electromagnet 10 will retain the key I) in the talking position until one or the other of the receivers is replaced, at which time the circuit of the electromagnet 10 will be broken and the key b restored to normal osition by means of the spring (not shown Should substation A originate the call the generator 49 will be rotated when a circuit will be completed from armature winding 48 of generator 49, line 50, magnet 10 contacts 69 and 70, contacts 64 and 71, bell 72, short circuit of armature winding 41 of generator 40, line 42 back to the other terminal of the armature of generator 49. The attendant will lift receiver 31 and throw the key upward as before when the talking circuit will be as previously described.

Should the exchange desire connection with the substation A the attendant after answering the exchange will move key a so as to connect contacts 80 and 81, and 82 and 83 respectively, whereby one coil of the bell 18 is joined across the exchange circuit to maintain the central apparatus energized, while he calls the substation A in the manner already described. When the station A replies, the attendant will move key bso that contacts 22 and 84, 69 and 85, engage respectively, and in so doing as described in connection with Fig. 2 the key a will be reset to normal by the engagement therewith of key I). The circuit will then be from central battery and one winding at the exchange 0, line 19, contacts 20 and 21, contacts 22 and 84, through short circult of armature winding 41 of generator 40, wire 42, microphone 51, receiver 52, contacts 53 and 46 of switch-hook 47 and through short circuit 48 of generator 49, line 50, electromagnet 10 with shunt 68 in parallel with it, contacts 69 and 85 to line 27. The electromagnet 10 will therefore hold the key operated until the circuit is broken at substation A, when the receiver 52 is replaced. The shunt 68 will maintain the talking efliciency and the microphone 51 will receive current from the central battery.

With the arrangement shown in Fig. 5 the circuits and operation is very similar to that described in connection with that of Fig. 4, and need not therefore be described further in detail. The exchange line 27 instead of connecting direct to contact 85 of key I; has included in it' the winding 101 and shunt 102 of rela 103, which is made slow acting in the wellown manner. Relay 103, which is energized when the substation A is connectedwith the central exchange, completes a local circuit from battery B contacts 66, 67, armature 109 of relay 103, contact 105, electromagnet 10 to battery B. Station A may therefore move the switch hook 47 to call the attention of the central operator without deenergi'zin the electromagnet 10.

It is o vious that various modifications may be made in the methods of carrying this invention into effect. For example the form of electromagnet which locks the key I) may be modified. Also it may be arranged that the local battery is connected across the loop instead of being in series in one side of the line. Also current may be supplied from the central exchange over a feeder wire.

What I claim and desire to secure by Letters Patent is, p

1. In apparatus of the class described, a

pair of double-throw key switches, and electromagnetic means for holding one of said switches in either of two operated positions, said last-mentioned switch being adapted to restore the other switch to normal position when it is thrown to one of its two operated positions.

2. In apparatus of the class described, an electromagnet, a slotted pole-piece therefor, and a ke switch carrying an armature projecting t rough said slot but normally out of contact with said pole-piece, said armature being adapted to engage with said polepiece when said switch is thrown into operated position, whereby said switch is electromagnetically held in operated position.

3. In apparatus of the class described, a pair of double-throw key switches, a switch hook, means controlled by said switch hook for restoring one of said switches to normal position when it has been operated in one direction, and means controlled by the other of said switches for restorin said switch when it has been operated in t e other direction.

4. In apparatus of the class described, a l and electromagnetic means for holding said pair of double-throw key switches, a switch second switch in operated position. 10 hook, means controlled by said switch hook In testimony whereof I have aflixed my for restoring one of said switches to normal signature in presence of two witnesses.

5 position when it has been operated in one WILLIAM AITKEN.

direction, means controlled by the other of Witnesses: said switches for restoring said switch when WALTER H. DERRIMAN,

it has been operated in the other direction, I ALBERT JONES. 

